1. Field of the Invention
The present invention relates to an electronic equipment, and, more particularly, to an electronic equipment having a device which is cooled down to an extremely low temperature so as to operate in a superconductive state.
2. Description of the Related Art
In recent years, radio receivers, with a high degree of reception sensitivity, for use at a mobile communications or satellite communications base station are developed.
For example, a radio receiver disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H10-126290 employs a superconductor filter. In this radio receiver, a decrease in the loss of filter is achieved, as compared to any other conventional radio receivers.
In this radio receiver, a low-noise amplifier which amplifiers a signal output from a filter is operated at a low temperature, thereby to reduce thermal noise.
To have a high degree of reception sensitivity, the radio receiver of the above publication includes a cooler which cools down a superconductor filter and the low-noise amplifier to an extremely low temperature.
Because a band pass filter is formed from a superconductor filter, the radio receiver exhibits steep attenuation characteristics over a pass band, and the band pass filter is likely to select signals at a predetermined frequency band.
In the case where a radio receiver includes a superconductor filter, it is necessary to control the temperature of the band pass filter to be constant.
It is because the pass band frequency of the band pass filter is determined based on the inductance of a filter circuit, and the penetration depth of the superconductor having an effect on the inductance changes depending on the temperature of the band pass filter.
Hence, there is employed a method for controlling the electric power to be supplied to the cooler, for example, while monitoring the temperature of the band pass filter.
While the cooler included in the radio receiver continues to operate for a long period of time, the level of the electric power to be input to the cooler may change as a result of a temporary variation in voltage or a sudden power failure. Besides, the radio receiver, in many cases, is arranged outside building, thus the cooling capacity of the cooler may change as an effect of a sudden variation in the outside temperature.
In this case, the problem is that the temperature of the band pass filter changes and its pass band frequency as well, thus the radio receiver does not perform a predetermined operation.
The present invention has been made in consideration of the above. It is accordingly an object of the present invention to provide an electronic equipment, which retains a temperature at which the electronic equipment can perform a predetermined operation, and which is not likely to be effected by some kind of temporary disturbance.
In order to achieve the above object, according to one aspect of the present invention, there is provided an electronic equipment comprising:
one or more electronic devices which are operable within a predetermined temperature range;
a cold stage which cools down said one or more electronic devices to such a predetermined operational temperature that said one or more electronic devices can perform a predetermined operation; and
a cold insulation member whose phase transition temperature is in a range between the predetermined operational temperature and an upper limit of the predetermined temperature range, and which is arranged adjacent to said electronic device, and whose phase changes so as to retain a temperature of said one or more electronic devices within the predetermined temperature range, and
wherein a part of said one or more electronic devices adjacent to said cold insulation member is formed from a material which is in a superconductive state at the predetermined operational temperature.
According to the above structure, while the phase of the cold insulation member is changing, the electronic equipment can retain the predetermined temperature at which the electronic device is operable, and a temporary disturbance is not likely to effect the operations of the electronic equipment.